Fixed hybrid dental attachment assembly and methods of use

ABSTRACT

A fixed hybrid dental attachment assembly is provided. The fixed hybrid dental attachment assembly includes an abutment member, a male member, and a cap. The abutment member has an outer locating surface portion projecting downwardly from an upper end. The male member for attachment to the abutment member has an upper end for engagement within a cap in a recess in a dental appliance, and a continuous, unbroken skirt projecting from the upper end of the male member for engagement over the outer locating surface of the abutment member. The skirt may have a rounded, convex outer surface, and the male member may be constructed from a PEEK material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 17/394,275, filed on Aug. 4, 2021. All references, includingpublications, patent applications, and patents, cited herein are herebyincorporated by reference to the same extent as if each reference wereindividually and specifically indicated to be incorporated by referenceand were set forth in its entirety herein.

TECHNICAL FIELD

Devices and methods provided herein relate to a dental attachmentassembly for anchoring a dental appliance with a base structure such asa tooth root or dental implant.

BACKGROUND

Standard dentures are fully removable dentures that are placed in themouth after all teeth have been removed. Once the mouth tissue hashealed, the dentures are placed. These dentures are held in place bysuction contact and/or denture adhesive. For a standard denture to beplaced any remaining teeth must be extracted and the patient will befitted for the device. Without the extracted teeth's previous support,the gum ridge will begin to collapse and the mouth will develop a sunkenlook. Since the gum ridge flattens over time and the tongue tends toknock standard dentures loose, such a device can become a nuisance atbest or even a serious inhibitor to such basic functions as eating andspeaking. These and similar minor disturbances in the oral cavity canconstitute a major disruption to one's quality of living.

There are generally two types of alternative dentures, fixed orremovable dentures, often referred to as overdentures. Overdentures forma gum-supported base onto which a removable denture can be placed;overdenture implants are typically performed on the bottom teeth.Implants are placed into the jawbone to serve as anchors for theoverdenture itself. Often the overdenture is made for the bottom teeth,since traditional dentures remain less stable on the lower palate thanthe upper due to the lower ridge's u-shape, lack of osmotic pressure,tongue movement, and other factors. After the implants are placed, therestoring dentist may use LOCATOR® attachment systems to attach theremovable prosthetic denture to the implants. The LOCATOR attachmentsensure that the denture will not dislodge unintentionally and will notinconvenience the patient by preventing sliding or shifting in themouth. Overdentures are designed to be removable by the patient fordaily hygiene maintenance.

The advantages of overdentures are manifold. Often people choose implantoverdentures over conventional dentures because implants offer aconservative way to add retention, stability, and comfort to theedentulous patient. Instead of sliding freely around the gum area, thedenture remains snugly in place in the mouth because it is anchored tothe implants. One way this benefits the patient is by allowing her tomaintain her dietary health. While someone with traditional denturesmust stay away from chewy or hard foods for fear of dislodging thedenture, someone with an implant-secured overdenture can maintain hisability to adhere to his regular diet, fully chew his food, and absorbvital nutrition.

Furthermore, the implants themselves help stop facial-contourdeterioration, improving not only the physical but also the mentalwell-being of implant overdenture wearers. Ordinary dentures causefacial bone loss, perpetuating jaw collapse and premature aging. Suchfacial bone collapse occurs because after one's teeth are removed andone begins to wear a denture, the denture speeds up bone loss bydeteriorating the bone ridges where the denture is placed. Moreover, thejaw area increasingly resorbs in the areas where the teeth have beenextracted due to lack of stimulation. Overdenture implants providesupport for the jaw and gum area, since the implants will naturallyintegrate with live gum and bone, fortifying the jaw line and preventingbone resorption and facial bone loss. Such osseointegration not onlykeeps the facial bones physiologically healthy, but it also improves thepsychological health of wearers by allowing them to speak, eat, smile,and maintain their natural appearance with increased confidence.

Overall, implant overdentures present a more comfortable, healthy, anddurable option than standard dentures. The implants keep the denturesecured in place, allowing the patient to converse with confidence,participate in normal social interactions, and even enjoy a diverse dietfor optimal nutritional health. Moreover, the implants keep the facialcontours and jaw line from collapsing, allowing edentulous patients tomaintain bone retention and actually strengthen the jaw line.

But overdentures are not without drawbacks. Dental anchoring orattachment assemblies are utilized to anchor the overdenture appliancewith a dental implant or tooth root, typically by fitting two or morepartially-movable components together to provide an improved fit andcomfort. In some assemblies, male and female parts have mating, snapengageable formations for releasably securing the male part to thefemale part. For example, the female part, which resides in theappliance or prosthesis, has a socket and the male part, which isanchored to the dental implant or tooth root has a head for snapengagement in the socket. But repeated impacts of the socket and head,as the prosthesis is removed and reattached, can damage the retentivehead of the male and cause wearing due to friction of the components asthey move. A compressible annular ring can be provided to absorb thefrictional forces and act as a cushion between the socket and the head;however, even the ring may wear out over a period of time and need to bereplaced, requiring regular maintenance of the dental anchoring assemblythat is uncomfortable and inconvenient for the patient. Furthermore, toallow the compressible annular ring to be easily removed and replaced,the ring can be provided with a securing mechanism on a mating surfacewith the socket (such as a threaded portion), which further adds to thecost and complexity of the dental anchor assembly.

FIGS. 15A and B illustrate removable overdenture assemblies. As can beseen the prosthesis 1900, comprises a gingival flange 1910 that coversand is supported by the gums 1908. Female caps 1902 a, b, c, and d areplaced within prosthesis 1900 and mate with male abutments 1904 a, b, c,and d to anchor the prosthesis 1900. Abutments 1904 a, b, c, and d aretypically screwed into implants 1906 a, b, c, and d. The caps 1902 a, b,c, and d form a retentive force with the abutments 1904 a, b, c, and dthat holds the prosthesis in place; however, the retentive force isnecessarily such that it can be overcome so the prosthesis can beremoved for daily cleaning. While four implant assemblies areillustrated in FIG. 15A, it is not uncommon for only two implantassemblies to be used for removable overdentures.

FIG. 15B is another example of a removable denture assembly that uses abar 1914 to form an implant-supported, removable denture assembly. Ascan be seen the bar includes, or couples with implants 1906 a, b, c, andd, and can accommodate abutments 1904 a, b, c, and d. Prosthesis 1900,with flange 1910, can then “snap” down on abutments 1904 a, b, c, and d.The assembly of FIG. 15A is referred to as an implant-retained dentureassembly, while the assembly of FIG. 15B is an implant-supported dentureassembly.

As noted above, an annular ring (not shown), or retention head asdescribed below with respect to FIGS. 6-10 , can be included within thecaps 1902 a, b, c, and d. But issues may still persist as described.

Another problem with removable denture assemblies is that over time thetissue can recede.

These issues can be addressed with permanent or fixed dentures, whichare basically denture devices that consist of a row of prosthetic teethconnected to a framework that is held in position by dental implants andis only removable by a clinician. A typical procedure for placement ofpermanent dentures involves an oral examination of the patient'sdentition, followed by scanning of the jawbone to determine the preciselocations for implant placements—two in the anterior region and two atthe back of the jawbone at minimum. The permanent dentures will beaffixed to the implants following the healing period, during which timethe implants would biologically fuse to the jawbone viaosseointegration.

FIGS. 16A and B illustrate various example fixed denture assemblies. Ascan be seen in FIG. 16A, prosthesis 2000 is similar to prosthesis 1900,but does not include a gingival flange. This is because prosthesis 2000does not come out and there must be some room to clean under prosthesis2000 and over gums 2008. But as with prosthesis 1900, prosthesis 2000can be attached to abutments 2004 a, b, c, and d, which can in turn bescrewed or otherwise couple with implants 2006 a, b, c, and d. Butagain, unlike the assembly of FIGS. 15A and B, prosthesis 2000 istypically affixed to the abutments 2004 a, b, c, and d via screws 2012that screw into abutments 2004 a, b, c, and d form the top of prosthesis2000.

FIG. 16B is another example of a fixed denture assembly that uses a bar2014, which is common. As can be seen the bar includes, or couples withimplants 2006 a, b, c, and d, and can accommodate abutments 2004 a, b,c, and d.

The screws 2012, abutments 2004 a, b, c, and d, and implants 2006 a, b,c, and d, are metal, which raises the cost, but also result in severalmetal on metal interfaces that can lead to alignment and seating issues.While the idea is that the fixed appliance 2000 is tightly coupled tothe base assemblies, i.e., abutments 2004, b, c, and d, and implants2006, b, c, and d, such that the appliance 2000 cannot move, there arealways, e.g., cantilever and other forces that act on the appliance2000. Moreover, it is sometimes necessary to remove a fixed dentalappliance, which can create wear on the metal on metal interfaces.Because the metal on metal interfaces are so rigid, and the appliance isnot supported by soft tissue as in the case of removable, these forcesare dissipated through the weaker appliance 2000, which can eventuallylead to cracking of the appliance 2000.

FIG. 16B illustrated another example fixed denture assembly thatincludes additional metal, screw retained parts 2005, which can increasecosts even further and further exacerbate the problems described.

Another problem with conventional fixed denture assemblies is the needto remove up to 15 mm of vertical bone height to accommodate the stackedcomponents and make room for the prosthesis.

Another problem with conventional fixed denture assemblies is related tothe labor intensive clinician appointment for hygiene. Retaining screwsmust be located, uncovered and removed to free the appliance forcleaning. The process then must be repeated in reverse to reattach theappliance. This procedure has a risk of appliance fracture due to thethrough holes required for screw access and is often avoided unlessanother problem requires it. This is a disadvantage for the patient andtheir overall oral hygiene.

SUMMARY

According to one aspect, a dental attachment assembly comprises anabutment member for attachment to a tooth root, implant, or adjacenttooth, a retention member for fixed, non-patient removable attachment tothe abutment member, and a cap configured for securing in the recess ina dental appliance. The abutment member may have an upper end, and anouter locating surface portion projecting downwardly from the upper end,the outer locating surface portion being positioned to project above atissue level when the abutment member is secured in a tooth root orimplant. The abutment member may have a head portion at the upper endand a shaft depending downwardly from the head portion. The shaft may beat a predetermined angle to the head portion (e.g., 10 degrees, 20degrees, 30 degrees, or aligned with the head portion). The retentionmember may have an upper end configured for engagement within a cap in arecess in a dental appliance, and a continuous, unbroken skirtprojecting from the upper end of the retention member for engagementover the outer locating surface of the abutment member, the skirt havinga rounded, convex outer surface, the retention member being constructedfrom a polyetheretherketone (PEEK) material or other rigid material suchthat it provides a retentive force of about 10 to 75 pounds. Theabutment member and retention member may have mateable snap-engagingformations for releasable snap engagement when the retention member isattached to the abutment member. In some embodiments, the abutmentmember may have a socket projecting inwardly from the upper end, of theabutment member and a retention head projects from the upper end of theretention member for releasable snap engagement in the socket. Theretention head may have a lower end, with the skirt extending downwardlybeyond the lower end of the retention head, whereby the skirt willcontact the abutment member before the lower end of the retention headreaches the socket on re-insertion of the retention member into theabutment member. The abutment member may have a weep hole connecting thesocket to the outside of the abutment member for allowing saliva toescape. In some embodiments, the mateable snap-engaging formations maycomprise an outwardly bulging portion of the outer locating surfaceportion of the abutment member and a corresponding concave ring portionof an inner surface of the skirt of the retention member. The cap maycomprise a cavity having a rounded concave inner surface for containingthe upper end of the retention member. The concave inner surface of thecavity may allow for releasable snap engagement over the rounded outersurface of the skirt. In some aspects, the cap may comprise a generallycup shaped member having a central longitudinal axis, a top wall and anannular side wall extending away from the top wall, the top wall andside wall having an outer surface shaped to engage with the recess inthe dental appliance, and wherein the cavity is configured for swivelengagement with the retention member adapted for non-swivel engagementover the outer locating surface of the abutment member attached to thetooth root, implant, or adjacent tooth. The top wall may have aninterior top surface with a concave recess extending radially in anannular path along an outer annular peripheral portion of the interiortop surface, the concave recess forming a curve having a first radius ofcurvature. The curve of the concave recess may continue along at leastpart of the inner surface of the side wall towards an open end of therounded, concave inner surface of the cavity. The curve may beconfigured to provide swivel engagement with the retention memberbetween a non-swiveled position in axial alignment with the centrallongitudinal axis of the retention member and a fully-swiveled positionin which the central longitudinal axis of the cavity is at an angle tothe central longitudinal axis of the retention member. The range ofswivel of the cap over the retention member may be between 10-30degrees, between 15-20 degrees, approximately 30 degrees, or at least 30degrees.

According to one aspect, a dental attachment assembly, comprising: anabutment member for attachment to a tooth root, implant, or adjacenttooth, the abutment member having an upper end, and an outer locatingsurface portion projecting downwardly from the upper end, the outerlocating surface portion being positioned to project above a tissuelevel when the abutment member is secured in a tooth root or implant; amale member (also referred to herein as retention member) for attachmentto the abutment member, the male member having an upper end comprising aswivel joint for swivel engagement within a cap in a recess in a dentalappliance, and a continuous, unbroken skirt projecting from the upperend of the male member for engagement over the outer locating surface ofthe abutment member, the skirt having a rounded, convex outer surface,the male member being constructed from a rigid material; the abutmentmember and male member having mateable snap-engaging formations forreleasable snap engagement when the male member is attached to theabutment member; the outer locating surface portion being outwardlytapered at least adjacent the upper end of the abutment member forcentering the male member over the abutment member as the members aresecured together; and a cap for securing in a recess in a dentalappliance, the cap having a cavity for containing said swivel joint, thecavity having a rounded, concave inner surface for releasable snapengagement over the rounded outer surface of the skirt, the swivel jointand cap cavity together comprising means for permitting swivelling ofthe cap over the male member relative to the dental appliance.

According to another aspect, a dental attachment assembly comprises: anabutment member with a first end shaped to attach to a tooth root,implant or adjacent tooth, and a second end with an outer locatingsurface, wherein the outer locating surface of the abutment member hasat least two axially spaced retention portions comprising two generallyrounded, annular projections; a retention member having a first end anda continuous, unbroken skirt extending from the first end defining aninner surface for engagement over the outer locating surface of theabutment member, the retention member being constructed from a rigidmaterial (e.g., PEEK) such that it provides a retentive force of about10 to 75 pounds, wherein the retention member has at least two axiallyspaced, snap engaging formations on the inner surface of the skirt forreleasable snap engagement with the respective retention portions of theabutment member, and wherein the axially spaced, snap engagingformations on the inner surface of the skirt comprise two spaced,annular grooves for snap engagement over the annular projections on theabutment member; and a cap with a rounded, concave inner surfacedefining a cavity to receive a swivel engagement with the retentionmember; wherein an interior top surface of the cavity includes a concaverecess extending radially along an outer periphery of the interior topsurface of the cavity. In some embodiments, the assembly can comprise acentral portion of the interior top surface that protrudes verticallyinto the cavity, and the retention member can be in direct contact withthe central portion. In some embodiments, a curve of the concave recesscontinues along a side wall of the rounded, concave inner surfacedefining the cavity. The concave recess can curve at a plurality ofvarying angles along the side wall and the interior top surface of thecavity. The concave recess can be composed of a series of consecutivetangent circular arcs, which can one or more of increase in size fromthe interior top surface to the bottom portion of the cap, and comprisedof circles of increasing size from a top portion of the cap to a bottomportion of the cap. The concave recess can provide a retention memberwith an angle correction of up to, for example, approximately 30degrees. The cap can have any suitable diameter and height, includingfor example, an outer diameter of approximately 5.4 mm, and a height ofapproximately 2.3 mm.

According to another aspect, a dental assembly comprises: a) anendosseous dental implant comprising: (i) a first end portion having atop and a bottom, the first end portion comprises: (1) an externalprojection extending from the top of the first end portion forreleasable engagement with an abutment member, wherein the abutmentmember has an external lower bevel portion; and (2) an annular cuffportion defining an annular seat having a recessed, inwardly taperedbevel surface, wherein the tapered bevel surface surrounds the externalprojection; and wherein the lower bevel of the abutment member contactsand seats on tapered bevel surface of the annular seat to form a line ofconnection when the abutment member is releasably engaged with theexternal projection, wherein the line of connection is located slightlybelow a patient's gum line when the implant is secured in the mouth ofthe patient; and (ii) a threaded post which extends from the bottom ofthe first end portion for direct engagement into the patient's bone ortissue; b) a retention member having a first end and a continuous,unbroken skirt extending from the first end defining an inner surfacefor engagement over the outer locating surface of the abutment member,the retention member being constructed from a rigid material (e.g.,PEEK) such that it provides a retentive force of about 10 to 75 pounds;and c) a cap configured for securing in a dental appliance and engagingthe retention member. It is contemplated that the threaded post can bestraight, or can be angled relative to at least one of the first endportion and the abutment member. For example, the threaded post can beangled between 10-20 degrees, about 15 degrees, between 25-35 degrees,or about 30 degrees relative to at least one of the first end portionand the abutment member. In some embodiments, the threaded postcomprises a single lead thread or multiple lead threads. In someembodiments, the threaded post comprises opposing axial cuts adapted forself-tapping into the patient's bone or tissue. In some embodiments, thedental implant has a maximum outside diameter between about 1.5 mm andabout 4.0 mm. In some embodiments, the threaded post comprises twosuccessive threads of different pitch. In some embodiments, the annularcuff portion may be of different heights to accommodate different tissuedepths. In some embodiments, the external projection can include atool-receiving bore extending inwardly from an upper end of theprojection.

According to another aspect, a dental assembly comprises: a dentalappliance comprising a first recess and a second recess; a first cap forsecuring in the first recess and a second cap for securing in the secondrecess; a first abutment member for attaching to a first tooth root,implant, or adjacent tooth, and a second abutment member for attachingto a second tooth root, implant, or adjacent tooth; a first retentionmember sized for engagement within the first cap, the first retentionmember having a first end and a continuous, unbroken skirt extendingfrom the first end defining an inner surface for engagement over theouter locating surface of the first abutment member, the retentionmember being constructed from a rigid material such that it provides aretentive force of about 10 to 75 pounds; and a second retention membersized for engagement within the second cap, the second retention memberhaving a first end and a continuous, unbroken skirt extending from thefirst end defining an inner surface for engagement over the outerlocating surface of the second abutment member, the retention memberbeing constructed from a rigid material such that it provides aretentive force of about 10 to 75 pounds. All suitable abutment members,caps, and retention members are contemplated, including any or all ofthe abutment members, caps, and retention members described above or inthe detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of embodiments of the present disclosure, both as to theirstructure and operation, may be gleaned in part by study of theaccompanying drawings, in which like reference numerals refer to likeparts, and in which:

FIG. 1 illustrates one embodiment of a dental anchoring or attachmentassembly that can be attached with an implant that can be anchored to abone or other base structure such as a tooth root, according to anembodiment;

FIG. 2 illustrates the external surface of the head of a retentionmember, according to an embodiment;

FIG. 3 illustrates another view of the external surface of the head ofthe retention member of FIG. 2 ;

FIG. 4 illustrates a dental attachment assembly in an angled, unattachedconfiguration, according to one embodiment;

FIG. 5 illustrates the dental attachment assembly in the angledorientation shown in FIG. 4 but where the retention member is nowsnap-fit into the socket of the abutment;

FIG. 6 illustrates a removable dental attachment assembly for attachinga dental appliance to an implant, according to one embodiment;

FIG. 7 illustrates a sectional view taken on line 7-7 of FIG. 6 , with aretention member shown separated, according to an embodiment;

FIG. 8 is a view similar to FIG. 7 , showing the retention member ofFIG. 7 aligning with the abutment member of FIG. 6 , according to anembodiment;

FIG. 9 is a view similar to FIGS. 7 and 8 , including a cap and showingthe retention member of FIG. 7 coupled to the abutment member of FIG. 6, according to an embodiment;

FIG. 10 is a sectional view showing a shortened form of the abutmentmember of FIG. 6 , according to an embodiment;

FIG. 11A illustrates another example embodiment of a removable dentalassembly, according to one embodiment;

FIG. 11B is an isometric view illustration of the cap of the dentalassembly of FIG. 11A;

FIG. 11C is an isometric cutout view illustration of the cap of thedental assembly of FIG. 11B;

FIG. 11D is a sectional view illustration of the cap and a retentionmember of the dental assembly of FIG. 11A;

FIG. 11E is a sectional view illustration of the cap of the dentalassembly of FIG. 11A illustrating consecutive tangent circle arcs whichare used to create an angle of a concave recess on an interior wall ofthe cap;

FIG. 11F is a sectional view illustration of the cap of the dentalassembly of FIG. 11A illustrating an angle of the concave recess;

FIG. 11G is a sectional view of the dental attachment assembly of FIG.11A in a fully swiveled position;

FIG. 12 illustrates a conventional Peek retention member that includes agap our slot cut into the retention member in order to allow for someresiliency;

FIG. 13 illustrates one embodiment of a dental anchoring or attachmentassembly, according to another embodiment;

FIG. 14A illustrates a dental anchoring or attachment assembly with alower portion configured to be straight;

FIG. 14B illustrates the assembly of FIG. 14A with a lower portionconfigured to be angled;

FIG. 14C illustrates the assembly of FIG. 14A with another lower portionconfigured to be angled;

FIG. 15A illustrates a removable overdenture assembly, according to anembodiment;

FIG. 15B illustrates a removable denture assembly that uses a bar,according to an embodiment;

FIG. 16A illustrates a fixed denture assembly according to anembodiment; and

FIG. 16B illustrates another fixed denture assembly, according to anembodiment;

FIG. 17 illustrates a fixed hybrid dental attachment assembly, accordingto an embodiment.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theaccompanying drawings, is intended as a description of variousembodiments, and is not intended to represent the only embodiments inwhich the disclosure may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof the embodiments. However, it will be apparent to those skilled in theart that embodiments of the invention can be practiced without thesespecific details. In some instances, well-known structures andcomponents are shown in simplified form for brevity of description.

The dental attachment assembly described in U.S. Pat. No. 9,931,181 (the'181 Patent), which is incorporated herein by reference as if set forthin full, functions similar to a fixed dental attachment system asdescribed above, yet can be more easily removed by a dental professionalusing a special tool and which overcomes many of the problems ofconventional fixed dental attachment assemblies. The dental attachmentassembly described in the '181 Patent is useful to attach a dentalappliance, not intended to be removable by the patient, such as adenture, with an implant and provide a retentive force of about 8 to 75pounds, while also providing ease of engagement of the retention memberwith the abutment due to the compressible nature of the materials usedand the friction-retained snap-fit of the ball and socket componentsincluded within the assembly.

As will be described in detail below, the retention member is formedfrom a compressible material—such as a polymer or soft metal—to allowthe retention member to compress and flex while being attached ordetached from an abutment secured to the implant. The compressible andflexible retention member can then be secured with the abutment at avariety of angles, which is often necessary when securing a dentalappliance to a plurality of implants extending at different anglesacross a person's upper or lower mandible. Additionally, thecompressible ball eliminates the need for a separate compressibleannular ring to be positioned in the socket of the abutment between theretention member and interior abutment walls, as well as the need for asecuring mechanism for securing the annular ring to the abutment walls.The dental attachment assembly is therefore easier to manufacture andrequires less maintenance once inserted.

FIGS. 1-5 herein are the same as FIGS. 1-5 of the '181 Patent. FIG. 1illustrates one embodiment of a dental anchoring or attachment assembly100 that can be attached with an implant (not shown) that can beanchored to a bone or other base structure (not shown) such as a toothroot. The assembly includes an abutment 102 that is secured to theimplant and a cap or denture attachment housing (DAH) 104 that issecured in a recess of a dental appliance. A retention member 106 servesto provide the frictionally-retained connection between the cap 104 andthe abutment 102. To this end, the retention member 106 includes a shaft108 that, e.g., has a threaded end portion 110 in a threaded connectionwith a corresponding threaded bore 111 in the cap 104. A second end ofthe shaft, which interfaces with the abutment 102, includes a head 112that is substantially spherical in shape and which is configured tocreate a frictional fit with an inward projection or barb 120 in asocket 114 found in an upper opening 116 of the abutment 102.

The head 112 includes a curved surface 118 configured to frictionallyengage an annular inward projection 120 in the socket 114, and a flatlower end face 119 with, e.g., an inwardly directed hexagonal orpolygonal shaped recess 121 for engagement with a suitable tool when theretention member 106 is threadably engaged in bore 111 of cap 104. Theinward projection 120 has an undercut 123 that is engaged with the head112. The socket 114 does not necessarily need to be curved to match thecurved surface 118 of the head 112. Instead, the head 112 is in contactwith the socket 114 only at projection 120 in most or all attachmentorientations. In the embodiment of FIG. 1 , the outer surface of thehead 112 is convex, while the outer end face 119 of the head is flat inorder to provide for a closer fit of the head 112 with the abutment 102.The inward projection 120 is configured to have a friction fit with thecorresponding diameter of the head 112 at the mouth of the socket 114.

One benefit of the compressible material for the retention member 106 isthat the diameter of the head 112 can be altered to increase or decreasethe retentive force provided by the frictional-fit or compression of thehead 112 engaging with undercut barb 123 of annular projection 120. Thegreater the maximum diameter of head 112, the higher the retentiveforce, since the inward projection 120 cuts further into the head whenfully engaged. A smaller diameter head 112 provides less retentiveforce. Retention force may also be varied by using different, softer orharder compressible materials for head 112, as described in more detailin the '210 Patent in connection with the modified embodiment of FIGS.31 to 35C therein.

FIGS. 2 and 3 illustrate the external surface of the head 112 of oneembodiment of retention member 106. The outer ball-shaped or convexcurved surface 118 can have a series of flats or flattened portions 119around the circumference of surface 118 to reduce the amount of frictionbetween the curved surface 118 of the head and the corresponding curvedsurface or projection 120 of the socket. In an alternative embodiment,no flats are provided and the head has a smooth outer convex surface. Asmooth convex surface increases the amount of friction between head 112and projection 120, since the projection digs more deeply into thecompressible surface of the head in the attached configuration of FIG. 1. Thus, one, two, or all of the following parameters can be used to varythe retention force of the head in the abutment socket: head diameter,head shape, and the selected compressible material of the head. Theretention force may vary from anywhere between about 10 to about 75pounds, although some embodiments may provide as little as about 1 poundof retention force for use in the initial positioning of the dentalappliance and dental anchoring device.

The cap 104 is configured with an annular internal surface 122 which maybe curved to engage with a corresponding curved outer surface 124 of theabutment, providing an additional frictional fit for the dentalattachment assembly.

In one embodiment, a ball flange 126 is provided on shaft 108 at apredetermined spacing below threaded portion 110. Flange 126 extendsperpendicular to the axial direction of the shaft 108 and acts as a stopby engaging an opposing surface 127 of the cavity in cap 104 whenthreaded stem 110 is threaded into bore 111. The ball flange 126 servesto help locate the ball 112 within the socket 114 and cap 104 andprevent vertical movement of the assembly.

In the embodiment described herein, the retention member 106 can beformed from a compressible or elastomeric material such as a polymer ora soft metal, non-limiting examples of which include polymers such aspolyether ether ketone (PEEK), polyoxymethylene or acetal polymers suchas Delrin®, and soft metals such as nickel titanium (nitinol), pink TiCN(titanium carbo nitride) or titanium. The soft metal can be a coating onthe surface of the head portion in some embodiments. In one embodiment,the surfaces may be coated with a gold nitride coating to reducefriction.

FIG. 4 illustrates the dental attachment assembly in an angled,unattached configuration prior to full insertion of head 118 in socket116, 114, illustrating the varying angles at which the retention member106 may be snap-fit into the abutment. In practical applications, theimplant may protrude from the bone or tooth root at varying angles fromthe ideal vertical angle due to the structure of the bone or theplacement of the implant during surgery. The dental anchoring orattachment assembly therefore corrects any angular displacement byrotation of the head 112 in the socket 114. In one embodiment, the angleof approach of the head with respect to the abutment may vary up toabout 20 degrees in any direction from the vertically-alignedorientation shown in FIG. 1 . In combination with another implant alsooffset at a similar angle, the dental anchoring device may thereforeprovide as much as about 40 degrees of angle correction.

FIG. 5 illustrates of the dental attachment assembly in the angledorientation shown in FIG. 4 but where the retention member 106 is nowsnap-fit into the socket 114 of the abutment 102. As illustrated in FIG.5 , the head 112 may be secured within the socket 114 despite thedifferential angle. Furthermore, the annular surface 122 of the cap 104is also still frictionally engaged around the outer curved surface 124of the abutment with the offset indicated in FIG. 5 , and the annularprojection 120 is frictionally engaged at an angle around the opposingannular surface portion of head 118.

While the dental attachment assembly was a huge step forward for fixeddental assemblies in that it eliminated weakening through holes in theappliance and replaced the screwed together interfaces with theretention member 106 made of compressible or elastomeric material suchas a polymer or a soft metal, non-limiting examples of which includepolymers such as polyether ether ketone (PEEK), polyoxymethylene oracetal polymers such as Delrin®, and soft metals such as nickel titanium(nitinol), pink TiCN (titanium carbo nitride) or titanium, it is notinterchangeable with a removable or fixed appliance and still requiresexpensive component swaps to convert from one to the other, and can havea restoration height of 15-18 mm.

FIGS. 6-10 are recreations of FIGS. 1-5 of U.S. Pat. No. 6,030,219 (the'219 Patent), which is incorporated herein by reference in its entirety,and which illustrate a removable dental attachment assembly 10 forattaching a dental appliance to an implant 12. The design illustrated inFIGS. 6-10 present improvements that overcome the deficiencies withremovable assemblies described above. The assembly comprises a femalesocket member or abutment element 14 and a male retention member orelement 16 which has a swivel engagement in a cap 18 secured in a dentalappliance or prosthesis. The female element 14 is of relatively strongmaterial such as titanium coated with titanium nitride, pink TiCN(titanium carbo nitride), DLC (diamond like coating) or similarmaterial. Element 14 has an enlarged upper end portion 20 having anupwardly facing socket 26, and a downwardly threaded shaft or stem 22for attachment to an implant fixture 12 secured in the bone of an upperor lower dental arch. In FIGS. 6-10 , the stem 22 is threaded forengagement in a threaded cavity in an implant fixture 12. It will beunderstood that the female element will be provided in multiple threadconfigurations and diameters for engagement in any of the variousimplant fixtures currently available on the market.

The upwardly facing socket 26 is of suitable shape and dimensions forreleasable snap engagement with a downwardly depending retention head 28on the male element 16. The mating shapes of the socket 26 and head 28are similar to that described in U.S. Pat. No. 5,417,570 (the '570Patent), the contents of which are incorporated herein by reference, andwill have a similar action. An outer locating surface 30 of the upperend portion 20 projects upwardly above the tissue level 32 when thefemale element is secured to an implant or tooth root, as bestillustrated in FIG. 9 . Locating surface 30 preferably has a slightinward taper from a position just above the tissue level up to the upperend of end portion 20. The surface portion 34 below the gum level may becylindrical or have a slight inward taper such that the diameter at thelower end 35 of upper end portion 14 matches that of the implant 12, asindicated in FIG. 9 .

A pair of diametrically opposed, axially extending notches 36 can beprovided on the locating surface 30. These are designed for engagementwith an insertion tool (not illustrated) for holding the implant orfemale element 14 and threading it into a matching socket in an implantfixture 12. The female element or abutment 14 also can have a weep hole38 connecting the socket 26 to the outer surface of element 14, as bestillustrated in FIGS. 6 and 7 .

Unlike retention member 106 described above, which must be fairlyinelastic in order to provide the retentive force needed for a fixedassembly, the male element 16 is formed of a material having someresilience, preferably nylon plastic that provides for some level ofelastic reformation when the denture is removed and reattached.

The upper surface 40 is generally fiat, and a skirt 42 projectsdownwardly from the upper surface 40 to surround the retention head 28.The retention head 28 has an outer shape substantially matching that ofthe socket 26. Socket 26 has a tapered leading edge or rim 44, a reduceddiameter portion 45, an enlarged ring groove portion 46, and a lowerchamfer edge portion 48. Head 28 of the male element has a matchingshape with a chamfer 50 at the lower end, an annular ring portion 52 ofenlarged diameter for snap engagement in groove portion 46, a reduceddiameter portion 53, and an outwardly tapered upper end portion 54.

The skirt 42 has a lower end 56 which projects below the lower end ofhead 28, and an inner surface 60 which is tapered, preferably at anangle of around 10°, and is also concave, as best illustrated in FIG. 9. The dimensions of the skirt and the head are such that the lower end56 of the skirt will contact locating surface 30 before the lower end ofthe head contacts the female element, as best illustrated in FIG. 8 .The outer surface 62 of skirt 42 is convex or rounded, for snap-fit,swiveling engagement in a cavity 64 of corresponding shape in the cap18, as best indicated in FIG. 9 . This provides a swiveling, rotationalmovement or hinging action at the cap, where the attachment is securedto the denture or appliance, reducing wear, in a similar manner to thatdescribed in the '570 Patent. The pivoting of the nylon or resilientmale in the metal denture cap 18 allows minor corrections fornon-parallel abutments, as well as providing a longer lasting, resilientconnection.

The denture or appliance can be removed repeatedly for cleaning, simplyby snapping male head 28 out of socket 26, and can then be re-inserted.On re-insertion in the direction of the arrow 65 in FIG. 8 , forexample, the user may fail to align head 28 co-axially with socket 26.In this case, the lower end of skirt 42 will contact one side of thelocating surface 30 before the head 28 reaches the socket. Furtherdownward movement in the direction of the arrow 65 urges the maleelement to one side, in the direction of arrow 66, to align head 28properly with the socket. Thus, the locator surface portion 30 of thefemale element together with the inner locating surface of skirt 42 actto urge the head 28 into proper alignment with the socket prior to snapinsertion in the socket. This avoids the problem of the nylon headpotentially hitting the tapered rim 44 of the socket if mis-aligned,which would eventually cause damage to the softer head and decreaseretention ability. The skirt and locator surface also allow easierlocation and insertion of the dental prosthesis by the patient.

The female element 14 can be provided in several tissue cuff heights tomatch the surrounding gingival level 32. The minimum height of theoverall attachment assembly is much lower than that of the arrangementas described in the '570 Patent and that of a fixed assembly such asdescribed with respect to FIGS. 1-5 . The minimum height for a non-hexedimplant abutment will be of the order of 1.75 mm, while the minimumheight for a hexed implant abutment will be around 2.75 mm, which willhelp in cases where the implant is at tissue level. This is lower thanthe height of all such attachments currently on the market today, andhas the advantage of providing a much lower profile and increasedpatient comfort. Other heights will also be provided depending on thedepth of the tissue. The low profile above the attachment is also betterfor tooth placement.

By providing external notches 36 for engagement with an insertion tool,rather than an internal hex indent or the like as in the '570 Patent,the height of the female element can be reduced. The notches allow thefemale element to be held firmly for threading into the implant fixture12.

The weep hole 38 is located above the tissue level and makes it easierfor saliva to escape from socket 26, reducing hydraulic pressure as aresult of the male head engaging in the socket. This also allows easierconnection of the male and female elements. Once the head 28 is in snapengagement in the socket, as in FIG. 9 , the skirt will only contact thelocator surface portion 30 at the lower end, while the concave innersurface 60 will be spaced from surface portion 30 along the remainder ofthe attachment, as best illustrated in FIG. 9 . This also enables easierinsertion of the head 28 into the socket once the parts are in properalignment.

FIG. 10 illustrates a modified female element or abutment 70 forattachment to a non-hexed implant (not illustrated). Element 70 will beused with the male element 16 of FIGS. 6-9 in a similar manner to hexedimplant abutment 14, and like reference numerals have been used for likeparts as appropriate. In this embodiment, head portion in FIG. 10 isshorter than in the previous embodiment, and the hex indent 72 of FIGS.6-9 is eliminated, with head portion 20 instead having a fiat, lowerannular face 74 which fits against the fiat upper face of the implant.

FIGS. 1-5 of U.S. Pat. No. 10,687,920 (the '920 Patent), which isincorporated herein in its entirety as if set forth in full, andrecreated here as FIGS. 11A-G illustrate another example embodiment of aremovable dental assembly that possess the advantages of the removableassembly depicted with respect to FIGS. 6-10 and as described in the'210 Patent. But the assembly described in the '920 Patent also allowsfor increased swivel adjustment. As shown in FIG. 11A and more clearlyin the isometric views in FIG. 11B and FIG. 11C, in one embodiment, aninterior top surface of the cap 1108 is configured with a concave recess1110 extending radially along an outer periphery of the interior topsurface of the cavity. The concave recess 1110 allows the cap 1108 toswivel at a much greater angle with respect to the retention member 1106and abutment 1104, which makes it easier for a person to secure thedental appliance onto the abutment 1104. A central portion 1112 of theinterior top surface of the cap 1108 protrudes vertically into the capcavity and minimizes vertical displacement between the retention member1106 and the cap 1108 that would have occurred without the presence ofthe central portion 1112. In this exemplary embodiment, the cap isapproximately 1.9 millimeters in height, although one of skill in theart will appreciate that the dimensions of the cap may vary.

In the embodiment illustrated in FIG. 11A, the retention member 1106 isretained by a skirt (or side wall) that projects from one end of the cap1108 for releasable engagement of the retention member 1106 with the cap1108, as disclosed in U.S. Pat. No. 6,981,871, incorporated herein byreference in its entirety. The outer locating surface of the abutment1104 has at least two axially spaced retention surfaces for mating, snapengagement with corresponding spaced snap engagement formations on theinner surface of the retention member 1106, to provide a stacked,external retention between the abutment 1104 and retention member 1106.

FIG. 11D illustrates a side cutout view of the cap 1108 and retentionmember 1106 in a non-swiveled position, which more clearly illustrateshow the retention member 1106 fits within the cavity of the cap 1108when no swiveling has occurred. The retention member 1106 is in contactwith the central portion 1112 of the interior top surface of the cap1108. Outer side walls of the retention member 1106 are generally curvedto match the curved surface of the inner side walls of the cap 1108, andthey may be in direct contact at a portion of the side walls at any oneposition to allow for ease of swivel without an excessive amount offriction.

In one embodiment, the concave recess 1110 is specifically designed witha curvature 1114 which may be formed using a series of consecutivetangent circular arcs formed from multiple circles of varying radii, asillustrated in FIG. 11E and FIG. 11F. In the embodiment illustratedherein, circles A, B, and C represent portions of the tangent circulararcs used to derive the curve 1114, although any plurality of circlesmay be used. The circles A, B, and C are arranged from large-to-smalldiameter from a bottom portion 1108B of the cap to a top portion 1108Aof the cap to form the varying angles of the curve 1114. As illustratedin FIG. 11G, the curve 1114 is designed to optimize the swivel of thecap 1108 around the retention member 1106 while maintaining engagementof the retention member 1106 within the cap 1108. Varying diameters ofeach of the circles may be used as long as the diameters are arrangedfrom large-to-small from a bottom-to-top direction along the interiorside wall of the cap. In the exemplary embodiment of FIG. 11E, theconcave recess 1110 is formed from circles A, B, and C with diameters of0.067, 0.083 and 0.186 inches, respectively (i.e. radii of curvature of0.034, 0.042 and 0.093 inches, respectively). Circle C has a diameterwhich intersects the concave recess 1110 on an opposing side of the cap,which therefore defines the diameter of the cap cavity. Each curvatureof each circle intersects with a different portion of the concave recess1110 to form a curved surface 1114 of varying degrees of curvature, asshown in FIG. 11F.

FIG. 11G illustrates one embodiment of the retention member 1106 andabutment 1104 in a fully swiveled position within the cap 1108, where aportion of the retention member 1106 has swiveled into the concaverecess 1110 in the cap 1108. The opposing side of the retention member106 has swiveled downward to the point that it is still retained withinthe cap 1108, which illustrates the complete range of swivel of the cap1108 in one direction. In this embodiment, the range of swivel S isapproximately 30 degrees with a cap having a diameter D of approximately5.4 millimeters (mm) and a height H of approximately 2.3 mm, althoughone of skill in the art will appreciate that these dimensions may bevaried and still achieve the same degree of rotation. The range ofrotation may reasonably extend to approximately 32 degrees (e.g.,between 15-20 degrees) and could be extended up to approximately 40degrees if the dimensions of the cap, retention member and abutment arealtered to allow for greater rotation—for example by increasing theheight of the cap and reducing the diameter of the abutment.

As with the assembly of FIGS. 6-10 , the retention member 1106 is madeof a resilient material such as nylon.

It is generally understood that harder, less resilient material such asPeek will not work for the retention member in a removable dentureassembly, because whatever material is used, it needs to repeatedlydeform and then reform as the dentures are removed and then reinstalled.Peek simply is not resilient enough. Certain manufacturers have usedPEEK for the retention member such with the Straumann® Novaloc®retentive system. But as illustrated in FIG. 12 , such PEEK retentionmembers must include a gap our slot cut into the retention member inorder to allow for increased resiliency.

While using a solid PEEK retaining member in a removable assembly iscounter intuitive, and would not work for a removable assembly, testinghas shown that the use of a solid PEEK retaining member with caps andabutments as illustrated, e.g., with respect to the embodiments of FIGS.1-5, 6-10, 11A-G, 13, and 14A-C can actually provide the benefits ofsuch removable assemblies, i.e., lower cost, no surgical plan and thelong term consequences thereof, lower restoration height, fewercomponents, elimination of screws and metal on metal interfaces, andgreater alignment margin, in a fixed assembly. In other words, it hasbeen shown that a PEEK retention member with the assemblies describedabove (e.g., in place of 16, 106, 1106, 1706 and optionally having thesame features and shapes of 16, 106, 1106, 1706) provide the retentionneeded for fixed applications.

This represents a major leap forward for fixed assemblies as it not onlyallows for the advantages of removable assemblies, but it provides hugeflexibility in restorative plans. In other words, the patient may startwith removable and transition to fixed (or vice versa), although aretrofit is likely required as noted below. But maybe more importantly,it allows for a transition in the event of a failed fixed restoration toa successful removable restoration with minimal procedures and cost. Afailed conventional fixed restoration failure can be emotionally andfinancially devastating as there is currently no ability to transition.The restoration plan can even change on the fly depending on surgicaloutcomes.

If a user has a removable assembly, then switching to a fixedimplementation, then additional implants (e.g., 1904) may be required.The flange 1910 can be removed in the short term and the same removableprosthesis 1900 can be used at least in the short term, while a fixedprosthesis is made.

As noted above, the placement of the implants is important, as theplacement and other factors can results in cantilever forces that cancause the prosthesis to crack. In certain instances, the patient's jawmay not allow an implant to be positioned far enough back in thepatient's jaw to sufficiently address the potential for such forces.While the retention member 1106 of the embodiments described withrespect to FIGS. 11A-G can allow for an angular displacement due to theup to 32 degrees swivel engagement (e.g., between 15-20 degrees swivelengagement), this may not be enough. Thus, the implant may need to beangled, such that the abutment is positioned even further back in thejaw.

For example, FIG. 13 illustrates an assembly 1700 in which the implant1702, screws into the abutment 1704, with retention member 1706, and cap1708. But as illustrated in FIGS. 14A-C, the lower portion 1802 ofimplant 1702 can be configured to be straight (FIG. 14A) or at variousangles such as 15 degrees (FIG. 14B), or 30 degrees (FIG. 14C). Assembly1700 can be similar to that described in, e.g., FIGS. 27-49 in U.S. Pat.No. 9,314,318, which is incorporated herein by reference as if set forthin full.

FIG. 17 illustrates a fixed hybrid dental attachment assembly 2100.Assembly 2100 comprises a cap 2108, retention member 2106, and abutmentmember 2104. Abutment member 2104 is configured for attachment to atooth root, implant, or adjacent tooth. Retention member 2106 isprovided for fixed, non-patient removable attachment to the abutmentmember. Cap 2108 is configured for securing in the recess in a dentalappliance. The abutment member 2104 may have an upper end, and an outerlocating surface portion being positioned to project above a tissuelevel when the abutment member is secured in a tooth root or implant.The abutment member 2104 may have a head portion at the upper end and ashaft depending downwardly from the head portion. The shaft may be at apredetermined angle to the head portion (e.g., 10 degrees, 20 degrees,30 degrees, or aligned with the head portion). It is contemplated thatabutment member 2104 can comprise any suitable abutment member,including any of the abutment members described in connection with otherembodiments described herein.

The retention member 2106 may have an upper end configured forengagement within a cap in a recess in a dental appliance, and acontinuous, unbroken skirt projecting from the upper end of theretention member for engagement over the outer locating surface of theabutment member, the skirt having a rounded, convex outer surface, theretention member being constructed from a PEEK material or other rigidmaterial such that it provides a retentive force of about 10 to 75pounds, for example about 25-75 pounds or about 50-75 pounds. Theabutment member 2104 and retention member 2106 may have mateablesnap-engaging formations for releasable snap engagement when theretention member is attached to the abutment member. In someembodiments, the abutment member may have a socket projecting inwardlyfrom the upper end, of the abutment member and a retention head projectsfrom the upper end of the retention member for releasable snapengagement in the socket. The retention head may have a lower end, withthe skirt extending downwardly beyond the lower end of the retentionhead, whereby the skirt will contact the abutment member before thelower end of the retention head reaches the socket on re-insertion ofthe retention member into the abutment member. The abutment member mayhave a weep hole connecting the socket to the outside of the abutmentmember for allowing saliva to escape. As shown in FIG. 17 , upper end ofthe retention member comprises an outer surface and an inner surface,and inner surface may lack a downwardly depending retention head (e.g.,28). The mateable snap-engaging formations may comprise an outwardlybulging portion of the outer locating surface portion of the abutmentmember and a corresponding concave ring portion of an inner surface ofthe skirt of the retention member.

The cap 2108 may comprise a cavity having a rounded concave innersurface for containing the upper end of the retention member. Theconcave inner surface of the cavity may allow for releasable snapengagement over the rounded outer surface of the skirt. In some aspects,the cap may comprise a generally cup shaped member having a centrallongitudinal axis, a top wall and an annular side wall extending awayfrom the top wall, the top wall and side wall having an outer surfaceshaped to engage with the recess in the dental appliance. The cavity maybe configured for swivel engagement or non-swivel engagement with theretention member, and the retention member may be adapted for swivelengagement or non-swivel engagement over the outer locating surface ofthe abutment member attached to the tooth root, implant, or adjacenttooth. In some contemplated embodiments, the top wall may have aninterior top surface with a concave recess extending radially in anannular path along an outer annular peripheral portion of the interiortop surface, the concave recess forming a curve having a first radius ofcurvature. The curve of the concave recess may continue along at leastpart of the inner surface of the side wall towards an open end of therounded, concave inner surface of the cavity. The curve may beconfigured to provide swivel engagement with the retention memberbetween a non-swiveled position in axial alignment with the centrallongitudinal axis of the retention member and a fully-swiveled positionin which the central longitudinal axis of the cavity is at an angle tothe central longitudinal axis of the retention member. The range ofswivel of the cap over the retention member may be between 10-30degrees, between 15-20 degrees, approximately 30 degrees, or at least 30degrees.

Assembly 2100 may also include implant 2102, and similarly to assembly1700, the lower portion of implant 2102 can be configured to bestraight, or at various angles such as between 15-32 degrees, especiallywhere the implant comprises an external projection extending from thetop portion for releasable engagement with an abutment member. However,it should be appreciated that assembly 2100 or a component/componentsthereof (e.g., cap 2108, retention member 2106) can be used inconnection with any suitable components of any of the assembliesdescribed herein.

It will be understood that the benefits and advantages described abovemay relate to one embodiment or may relate to several embodiments.Aspects described in connection with one embodiment are intended to beable to be used with the other embodiments. Any explanation inconnection with one embodiment applies to similar features of the otherembodiments, and elements of multiple embodiments can be combined toform other embodiments. The embodiments are not limited to those thatsolve any or all of the stated problems or those that have any or all ofthe stated benefits and advantages.

The preceding detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. The described embodiments are not limited to usage inconjunction with a particular type of dental attachment assembly foranchoring a dental appliance with a base structure such as a tooth rootor dental implant. Hence, although the present embodiments are, forconvenience of explanation, depicted and described as being implementedin a dental attachment assembly for anchoring a dental appliance with abase structure such as a tooth root or dental implant, it will beappreciated that it can be implemented in various other types of dentalattachment assembly for anchoring a dental appliance with a basestructure such as a tooth root or dental implant. Furthermore, there isno intention to be bound by any theory presented in any precedingsection. It is also understood that the illustrations may includeexaggerated dimensions and graphical representation to better illustratethe referenced items shown, and are not considered limiting unlessexpressly stated as such.

What is claimed is:
 1. A dental attachment assembly, comprising: anabutment member for attachment to a tooth root, implant, or adjacenttooth, the abutment member having an upper end, and an outer locatingsurface portion projecting downwardly from the upper end, the outerlocating surface portion being positioned to project above a tissuelevel when the abutment member is secured in a tooth root, implant, oradjacent tooth; a first retention member for fixed, non-patientremovable, attachment to the abutment member, the first retention memberhaving an upper end configured for engagement within a cap in a recessin a dental appliance, and a continuous, unbroken skirt projecting fromthe upper end of the first retention member for fixed, non-patientremovable engagement over the outer locating surface of the abutmentmember, the skirt having a rounded, convex outer surface, the retentionmember being constructed from a polyetheretherketone (PEEK) materialsuch that it provides a retentive force of about 10 to 75 pounds, suchthat upon engagement over the outer locating surface portion of theabutment member, the first retention member is non-patient removablefrom the abutment member; the abutment member and the first retentionmember having mateable snap-engaging formations for snap engagement whenthe first retention member is attached to the abutment member; whereinthe cap is configured for securing in the recess in the dentalappliance, and comprises a cavity for containing said upper end of thefirst retention member, the cavity having a rounded, concave innersurface for releasable snap engagement over the rounded outer surface ofthe skirt of the first retention member; and wherein the abutment memberis sized and dimensioned for engagement with a replacement retentionmember made of a more resilient material than the first retention memberand having a second end and a continuous, unbroken skirt extending fromthe second end configured for patient removable engagement over theouter locating surface of the abutment member, in place of the firstretention member.
 2. The assembly as claimed in claim 1, wherein theabutment member has a socket projecting inwardly from the upper end, ofthe abutment member and a retention head projects from the upper end ofthe retention member for releasable snap engagement in the socket. 3.The assembly as claimed in claim 2, wherein the retention head has alower end, and the skirt extends downwardly beyond the lower end of theretention head, whereby the skirt will contact the abutment memberbefore the lower end of the retention head reaches the socket onre-insertion of the retention member into the abutment member.
 4. Theassembly as claimed in claim 2, wherein the retention head does notproject downwardly beyond the lower end of the skirt, whereby the lowerend of the skirt contacts the abutment member prior to any other part ofthe attachment assembly.
 5. The assembly as claimed in claim 1, whereinthe abutment member has a weep hole connecting a socket projectinginwardly from an upper end of the abutment member to the outside of theabutment member for allowing saliva to escape.
 6. The assembly asclaimed in claim 1, wherein the mateable snap-engaging formationscomprises an outwardly bulging portion of the outer locating surfaceportion of the abutment member and a corresponding concave ring portionof an inner surface of the skirt of the first retention member.
 7. Theassembly as claimed in claim 1, wherein the abutment member comprises agenerally cylindrical head having a convex outer surface portionadjacent said upper end, and the first retention member is generallycup-shaped with an internal cavity for fitting over said head, the skirthaving a concave inner surface portion for snap engagement over saidconvex outer surface portion to secure the members together, said convexand concave surface portions comprising said mateable snap engagingformations.
 8. The assembly as claimed in claim 1, wherein the abutmentmember has a head portion at the upper end and a shaft dependingdownwardly from the head portion.
 9. The assembly as claimed in claim 8,wherein a longitudinal axis of the shaft does not form a straight linewith a longitudinal axis of the head portion.
 10. The assembly asclaimed in claim 9, further comprising a second abutment member and athird abutment member, wherein a longitudinal axis of the shaft of theabutment member forms a straight line with a longitudinal axis of thehead portion, wherein the second abutment member has a second shaft anda second head portion and wherein a longitudinal axis of the secondshaft is at an angle of 10° to a longitudinal axis of the said secondhead portion, and wherein the third abutment member has a third shaftand a third head portion, and wherein a longitudinal axis of the thirdshaft is at an angle of 20° to a longitudinal axis of the said thirdhead portion.
 11. The assembly as claimed in claim 8, wherein the headportion comprises the outer locating surface portion, and wherein theouter locating surface portion is convex.
 12. The assembly as claimed inclaim 1, wherein the cap comprises a generally cup shaped member havinga central longitudinal axis, a top wall and an annular side wallextending away from the top wall, the top wall and side wall having anouter surface shaped to engage with the recess in the dental appliance,and wherein the cavity is configured for swivel engagement with thefirst retention member adapted for non-swivel engagement over the outerlocating surface of the abutment member attached to the tooth root,implant, or adjacent tooth; the top wall having an interior top surfacewith a concave recess extending radially in an annular path along anouter annular peripheral portion of the interior top surface, theconcave recess forming a curve having a first radius of curvature; andthe curve of the concave recess continuing along at least part of theinner surface of the side wall towards an open end of the rounded,concave inner surface of the cavity; and wherein the curve is configuredto provide swivel engagement with the first retention member between anon-swiveled position in axial alignment with the central longitudinalaxis of the retention member and a fully-swiveled position in which thecentral longitudinal axis of the cavity is at an angle to the centrallongitudinal axis of the first retention member.
 13. The assembly ofclaim 1, wherein the upper end of the first retention member comprises aswivel joint, and wherein the swivel joint and cap cavity togetherpermit a swivelling of the cap over the first retention member.
 14. Theassembly of claim 13, wherein a range of swivel of the cap over thefirst retention member is between 15-20 degrees.
 15. The assembly ofclaim 13, wherein a range of swivel of the cap over the first retentionmember is approximately 30 degrees.